An investigation of the effect of drying methods on the nutritive value of forage grasses

ABSTRACT

Drying methods have been identified as a critical factor in forage evaluation because there are changes in their chemical components that are affected by different drying temperatures. The study evaluated the effect of three drying methods (sun-drying, shade-drying and oven-drying (60°C) on the chemical components of three local grass species (Pennisetum purpureum, Brachiaria ruziziensis and Brachiaria arrecta) grown under tropical conditions. The objective was to determine how drying methods influence the nutritive value of forage grasses to optimize feeding practices. The harvested grass samples were dried to a constant weight under the three drying methods before being milled and then subjected to chemical analysis. Dry matter (DM), organic matter (OM), ash, ether extract (EE), crude fibre (CF), and nitrogen free extracts (NFE) were determined. Across drying methods, the DM content was highest (p<0.05) in B. ruziziensis (908 g/kg DM). The OM of the oven dried species was significantly higher in B. ruziziensis (885 g/kg DM) when compared to the species of B. arrecta (867 g/kg DM) and P. purpureum (859 g/kg DM). The CP content was highest (p<0.05) in B. ruziziensis (123 g/kg DM) (shade dried) and lowest (p<0.05) in B. arrecta (87.6 g/kg DM) (sun-dried). Across drying methods, the CF content was highest (p<0.05) in B. arrecta (367 g/kg DM) (oven dried) and lowest (p<0.05) in P. purpureum (264 g/kg DM) (shade dried). Species demonstrated higher levels of OM, CP, and lowest CF levels under shade-drying when compared to other drying methods. It was concluded that drying methods do influence the chemical components of grass species with shade-drying, indicating a greater potential for laboratory analyses and field processing.

Keywords: Chemical composition, drying temperatures, fibre, forages, sun-drying, shade-drying.